If I do and nslookup on an IP or use nmap –sL for a range it only returns the fist DNS name it finds for that IP, anyone know a quick way to find more than one?

For example, lets say IP maps to srv.myorg.com. Some use also used a dynamic DNS service to map the same IP to myownedbox.dyndns.org. If it do an nsloookup on just I just see the srv.myorg.com, is there a way to use nslookup or dig to look for more than just the first mapping?